Water-responsive recyclable hydrogel enabled by chain-dispersion regulation of cationic guar gum for flexible multifunctional sensor

Abstract

Development of hydrogel strain sensors that simultaneously possess high mechanical strength and excellent recyclability remain challenging due to the intrinsic conflict between them. Herein, we develop a multifunctional hydrogel by simultaneously regulating molecular chain dispersion and constructing a dual-network structure. The acidic environment arising from Fe³⁺ hydrolysis and partial acrylic acid (AA) ionization may enhance cationic guar gum (CGG) chain hydration, thereby reducing interchain entanglement and aggregation. Meanwhile, the Fe³⁺/sodium lignosulfonate (SL) redox pair participates in the in-situ polymerization of AA to generate a dense polyacrylic acid (PAA) network interlocked with the well dispersed CGG chains, substantially reinforcing the hydrogel. The Fe³⁺ associated acidic environment is expected to facilitate CGG re-dispersion during water-responsive recycles. The resulting hydrogel sensor exhibits strong adhesiveness and self-healing capability, as well as high sensitivity and stable signal output under various strain conditions. Even after three recycling cycles, the hydrogel retains over 83% of its mechanical and sensing performance, indicating good performance retention and recyclability.